In 1986 (Sederberg & Parry 1986) presented a technique
for deforming solid 3D geometric models in a free–form
manner. First, a local coordinate system is imposed on a
parallelpiped region. Next, they impose a grid of control
points on the parallelpiped region. That way the deformation
is specified by movements of the control points. In fact,
mathematically, the deformation function is defined in terms
of a tensor product trivariate Bernstein polynomial in which
the coefficients of the Bernstein polynomial are actually the
control points of the grid.